ABSTRACTS OF TECHNICAL ARTICLES 459 



lower-molecular- weight fractions were soft and sticky. The tensile strength 

 of vulcanizates from the high fraction was somewhat greater than that of 

 the whole polymer, but the modulus was considerably increased. For the 

 low-molecular-weight polymer both tensile and modulus values were much 

 lower. Vulcanizates prepared by mixing natural rubber and gutta-percha 

 hydrocarbons show lower strength than either of the hydrocarbons sep- 

 arately tested in the same formula. 



